LED Display Lighting

August 4, 2009

LED Display Luminance and Color Uniformity

LED Display Manufacturer for Luminance and Color Uniformity:

1. When we Manufacture LED large display, the first choice in accordance with the brightness of LED indicators or led display module, followed by the choice of products based on red, green and blue color brightness than to determine what kind of color as the base, the general is a low brightness, as Benchmark light, when the benchmark has reached a maximum brightness, the adjustment of another (color) or two (full color). When two-color led display screen is in most cases to green as the base, adjusting the red diode current. General is to reduce the operating current to balance the color yellow for the adjustment of standards, this should reduce the brightness of the led  video display screen. To display the best color balance adjustment, you will reduce the led screen brightness. If the led RGB display brightness in order to achieve the requirements of each color have a maximum brightness, then lost the balance of colors, such as: two-color screen reddish yellow, or green side.
Low-level TTL output is about 0.4V, for irrigation if the current input, modify it by adding the maximum normal current 35mA, when more than this current, the output low-level increased, with the increase in current, constant low-level output higher output voltage that is greater than 0. 4V circuit is still working correctly. Show circuit in the scan, the working current of 20mA to meet the requirements of control of red, because red is relatively high brightness LED; green LED is higher than the operating current 20mA, current about 30 ~ 50mA in between, at this time, 74HC595 output voltage should be increased, because there 74HC595 output resistance, and non-linear change.
2. Dynamic scanning circuit scans, static-driven manner. Display by the display module to scan the frequency of structural limitations, each module there are 8 × 8 months LED display the entire line of data of all modules in series, the data is updated once a long time, when the scanning frequency of 100Hz, the entire led screen brightness will be reduced. If the lower screen of the scanning frequency, indicating lower brightness. Experiments show that sweeping depiction of the relationship between frequency and the color is relatively small.
So,After two-color LED display on the design and analysis, the effective adjustment of the technical parameters of the circuit, to be a better led display sign. Facts have proved that the rational analysis of the technical characteristics of the circuit, so that the work of the best circuits in the state, will be able to achieve the desired effect. 74HC595 companies choose a different circuit, different effects, in a led full color display of as much as possible to choose the same circuit, to avoid influence by the circuit parameters showed different results.
LED display board design and manufacturing is an important condition for the cost of production, therefore, the choice of components in the process of meeting the requirements, select the price low. In this paper the technical design and analysis on the basis of the circuit will adjust to display the best effect, to create a performance / price ratio of the led display panel, with market competitiveness.

August 3, 2009

The LED for Full color led display screen

A good environment for the use of methods and the LED for high-quality long-term maintenance LED Display Screen  is also very important:

1, anti-static for LED Video display

     LED Display assembly plant should have a good anti-static measures. Special anti-static and anti-static flooring, anti-static soldering iron, anti-static Taiwan pad, anti-static ring, anti-static clothing, humidity control, equipment grounding (especially the foot-cut machine) are the basic requirements, and regular use of electrostatic detection instrument .

2, Wave soldering temperature and time for Outdoor led display

     To strictly control the solder wave front of the furnace temperature and time have been proposed as follows: preheating temperature 100 ℃ ± 5 ℃, the maximum does not exceed 120 ℃, and the preheating temperature rise for a smooth, welding temperature of 245 ℃ ± 5 ℃, welding time does not recommend more than three seconds, after the furnace must not have been the impact of vibration or LED, until the restoration of normal temperature state. Wave soldering machine to regular testing temperature parameters, which is decided by the characteristics of LED, and overheating or temperature fluctuations will directly damage the quality of LED or LED hidden dangers, especially for small size, such as 3mm round and oval-shaped LED.

3, The design of current LED Display sign

     The nominal LED current is 20mA, the maximum use of general recommendations for the current nominal value of not more than 80 percent, especially for small screen space point, as a result of poor thermal conditions, but also reduce the current value. Based on experience, as the red, green and blue LED decay rate of the inconsistency, targeted to reduce the blue and green LED’s current value, in order to maintain white balance after the prolonged use of display consistency.

5, Mixed light for LED Display board

     With a different color LED brightness profile of the need for mixing light, or designed in accordance with the laws of discrete interpolation interpolation map lights lights, the entire screen in order to ensure the consistency of the brightness of each color. If there are problems in this process, there will be Indoor LED display brightness inconsistent local phenomenon, a direct impact on the effect of LED display screen.

5, Control of vertical light for LED Display panel

     LED for the line, the heaters have sufficient technology to ensure perpendicular to the PCB board LED. Any deviation will affect LED brightness has set a good consistency, the color appears inconsistent brightness. 

    6, Thermal design for RGB led display

     LED work at the fever, the temperature is too high attenuation LED will affect the speed and stability, so the heat PCB board design, thermal design of ventilation box will affect the performance of LED.

     7,Loose Soldering control for led display factory

     LED display in the LED does not shine, they often have more than 50% probability for all types of  Loose Soldering caused, such as the LED pin Loose Soldering, IC pin  Loose Soldering, Pai Pin  Loose Soldering such as the mother. The improvement of these issues need to strictly improve the process and to strengthen quality inspection to resolve. Vibration in front of the factory is quite a good test. 

    8, Driver circuit design for led screen

     LED Display module on board the drive arrangement drives also affect the brightness of the LED. As the drive output current in the PCB board transmission distance too far, will make transmission path pressure drop is too large, the impact of the normal LED operating voltage to reduce its brightness. We often find that the LED display module brightness around the middle lower than that for this reason. Therefore, to ensure consistency of display brightness, it is necessary to design a good distribution of drive circuit.

July 23, 2009

LED Video Display’s Inspection

The way of how to inspect the led video display:

1 . LED display board hardware environment:Using our eyes to check the hardware of led matrix display.

2 . LED displays software environment: using the eyes to check the software of  LED RGB display environment.

3 . Structure and appearance: Using eyes to check the structure and appearance for led displays.

4 . Safety requirements:
(1) Connect the ground to check the LED display screen.
(2) Checking  the security tags with visual inspection of the security tag  LED screen.
(3) LED Screens-to-ground leakage current at 1.1 times rated power supply voltage, testing LED display power cord between the metal frame-to-ground leakage current.
(4) According to the Anti-electric intensity LED display’s power switch position, power input or with the metal frame structure of hit pieces of metal between the imposition of 1500V (AC RMS), 1min.
(5) High Temperature  of LED display Panel in the workplace after an hour ,then test the working temperature.

6.  Color uniformity:Using eyes or software to test  the uniformity of LED display sign.

7.  LEDs out of control: Using eyes or software to check the leds that is out of control or different colors.

8.  Consumption: Power on the  full color LED display ,then Measuring the power consumption.

More ways will be coming for LED Display boards.

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